1. Field of the Invention
The present intention relates to a semiconductor device manufacturing unit and a semiconductor device manufactured by using the same, in particular, relates to a semiconductor device manufacturing unit characterized by the internal structure which is used to manufacture a semiconductor device by carrying out etching and film formation on a substrate by means of a plasma discharge of a reactive gas as well as a semiconductor device manufactured by using this semiconductor device manufacturing unit.
2. Description of the Related Art
There is a plasma reactive unit wherein the uniformity of etching and film formation is improved in a plasma chemical technology as a conventional semiconductor device manufacturing unit (for example, see Patent Reference 1).
[Patent Reference 1] Japanese Unexamined Patent Publication 2002-270527
As described in Patent Reference 1 a vertical type semiconductor device manufacturing unit as shown in FIG. 4 is known as a conventional general semiconductor device manufacturing unit.
A cathode 2, an anode 4 and a heater 24 for heating a substrate are fixed as structures to walls of a chamber that is subjected to the influence of external atmosphere in this semiconductor device manufacturing unit. The cathode 2 and the anode 4 make a plasma discharge occur and form walls of the chamber.
A structure made of an insulator is provided between the above described structures and the cathode 2 in an intervening form. Thus, this structure supports the cathode 2 and the anode 4 against the walls of the chamber.
An exhaust outlet is provided in the direction of one side around the periphery of the plasma discharge region formed between the cathode 2 and the anode 4. A cooling part 14 is provided to the lower portion of the cathode 2 and on the wall of the chamber. A glass substrate 1, which is an object to be processed, is fixed to a holder and the outer periphery of this holder is secured to the chamber walls.
Furthermore, the entirety of the chamber is formed of an aluminum alloy and the vacuum sealed portion of the cathode 2 and the vacuum sealed portion of a heater 24 which are effected by reactive radicals are covered with fluorine based rubber sealing material such as Kalrez in the case wherein an etching gas is utilized as a reactive gas.
Such a semiconductor device manufacturing unit is described below more concretely. That is to say a chamber is prepared as a reactive vessel and the anode 4 is placed inside thereof. The anode 4 makes contact with the heater 24 for heating the glass substrate 1, which is an object to be processed, to a constant temperature, for example 100° C. to 600° C.
Stainless steel, aluminum alloy or the like is utilized for the chamber and the anode 4, and ceramics or the like is utilized as a heat insulating material. Furthermore, the cathode 2 is placed so as to face the substrate 1 and this cathode 2 is supported by a cathode support 5 made of an insulator so as to be electrically insulated from the surrounding.
Here, it is necessary to set the interval between the cathode 2 and the anode 4 with a high precision in order to form a film with a uniform film thickness and film quality. Therefore, the cathode 2 is fixed by screwing peripheral portions thereof at regular intervals.
Stainless steel, aluminum alloy or the like is utilized as the material of the cathode 2. In addition, a great number of micro through holes are created in the surface of the cathode 2 facing the substrate 1 by means of piercing processing. The reactive gas supplied from a reactive gas introducing pipe 10 can be uniformly supplied to the surface of the substrate 1 by means of these through holes.
The substrate 1 is supported by a substrate support 15 in a stable manner and is placed on the surface of the anode 4 in the case of such a vertical type semiconductor device manufacturing unit. The cooling part 14 is placed outside of the heater 24 in order to restrict an increase of temperature in the chamber or of the vacuum sealing portions. This is because rubber sealing material such as Viton and Kalrez is used for the vacuum sealing portions and it is particularly necessary to cool these portions sufficiently.
An exhaust pipe 9 used for discharge space, a pressure controller 22 and a vacuum pump 21 are provided in order to freely control the pressure of the reactive gas within the chamber. A harm abatement device 23 for removing harmful substance from the exhaust gas is connected to the vacuum pump 21. In addition, a plasma exciting power supply 12, which is a power supply of high frequency and an impedance matching device 13 are provided in order to supply power of high frequency to the cathode 2.
Such a configuration makes a glow discharge occur between the cathode 2 and the anode 4 under the condition wherein the pressure of the reactive gas is controlled so that an amorphous film or a crystal film is formed on the substrate 1.
Several problems as described below arise with the conventional semiconductor device manufacturing unit described above.
The cathode 2, the anode 4 and the heater 24 for heating a substrate are fixed to the walls of the chamber causing an increase in thermal conduction to the outside and therefore a grounding and a cooling device (the cooling part 14) for the sealing portions become necessary. In addition, the cathode 2 is used as a wall of the chamber that is affected by the external atmosphere even though the cathode itself is required to be highly insulated and therefore, the cathode 2 becomes the large structure, and parts thereof become expensive and it becomes necessary to cool the cathode from the rear side by means of the cooling part 14. The heater 24 is also connected to a wall of the chamber and therefore, it becomes necessary to cool this connection portion.
Though the cathode 2 is supported by a wall of the chamber via a structure made of an insulator, it is difficult to secure the distance for grounding of this wall against the introduction of power and therefore, the plasma discharge is also easily affected by this wall. Though it is necessary to place the chamber wall as far away as possible from the cathode 2 in order to restrict such an influence to the minimum, such an implementation directly causes an increase in size of the chamber and therefore becomes a factor in the increase of cost.
In addition, the cathode 2 which is a structure of large scale must prevent leakage of the reactive gas in addition to secure of an electric insulation vis-à-vis the chamber wall and therefore vacuum sealing parts of a large scale become necessary leading to a great increase of cost.
Furthermore, though a rubber sealing material such as Viton or Karlez is used for the vacuum sealing portions in the case wherein a fluorine based etching gas is utilized as the reactive gas, effects of fluorine radicals are inevitable to the sealing portions of the cathode 2 and the anode 4 in the vicinity of the plasma discharge region and therefore, an expensive Karlez must be used.
In addition, an exhaust outlet is provided for only the direction of one side in the surrounding of the plasma discharge region and therefore, the conductance of the reactive gas is reduced, thereby making it difficult to replace a large amount of gas.
Moreover, the plasma discharge region is limited to one side of the front because power is introduced from the rear side. In addition, a problem with an insufficient grounding arises in the case of a vertical type substrate setting wherein the surrounding of the substrate 1 is fixed.
The present invention is provided in view of such circumstances and an object thereof is to provide a semiconductor device manufacturing unit wherein a cathode and an anode can be placed in a simple structure, wherein excellent film deposition and film thickness distribution can be gained and no cooling device is required so that the entire structure of the unit is simplified and reduction of cost can be implemented as well as to provide a semiconductor device manufacturing method using such a unit.